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Technical Backfires

Discussion in 'Traditional Hot Rods' started by dwleo, Mar 25, 2017.

  1. dfriend
    Joined: Mar 7, 2012
    Posts: 20

    dfriend
    Member
    from B.C.canada

    Hi
    Check your power valves unless you have back fire checks in the carb. You say you think it is loading up.
     
    Boyd Wylie likes this.
  2. krylon32
    Joined: Jan 29, 2006
    Posts: 9,397

    krylon32
    ALLIANCE MEMBER
    from Nebraska
    1. Central Nebraska H.A.M.B.

    My deuce 3 window does something similar, runs fine until it warms up then starts to pop an crackle out of the left tailpipe. I've had several motor heads listen and of course they all have a different opinion. Seems to boil down to a carb problem. 650 Edelbrock on a 300 horse 327. Hopefully we'll get is solved shortly?
     
  3. dwleo
    Joined: Aug 10, 2014
    Posts: 47

    dwleo

    It has been suggested that it is the power valve in the carb that is screwed and done probably during a backfire in the carb when the timing was wonky.
    Thoughts?
     
  4. tinkirk
    Joined: Jan 16, 2017
    Posts: 111

    tinkirk

    what's the voltage going to the distributor, like do you have a ballast resistor hooked in line
     
  5. FrozenMerc
    Joined: Sep 4, 2009
    Posts: 3,093

    FrozenMerc
    Member

    Why are we lashing valves with hydraulic lifters???
     
  6. The above is most likely the when of the problem.
    You need to look at this "looseness" that occurred. What is that????
     
  7. FrozenMerc
    Joined: Sep 4, 2009
    Posts: 3,093

    FrozenMerc
    Member

    My guess is 31Vicky is pointing you in the right direction. After the cam break-in you had to "relash the valves" with hydraulic lifters??? Sounds like a lobe or 2 got wiped out to me.

    Did you drop the oil after the break-in? Was it all sparkly???
     
    Last edited: Mar 28, 2017
  8. They don't get loose,
    Something is wrong if they do.
    The list of possible somethings are :
    Excessive wear on lobes or lifters ( been known to happen on break in)
    Bent push rods
    Pulled studs
    Stripped or non locking nuts on the rockers.

    The other possible explanation is that they were never adjusted properly to begin with but That wouldn't be or shouldn't be stated as all was well and then a looseness occurred. If they were never adjusted correctly on break in start up the the loose ones would clack like crazy and the over tight ones would hold valves open, backfire or cause a cylinder miss and high probability of whipped out cam or lifters. I'm more than reasonably certain it wouldn't be running smoothly
     
  9. dwleo
    Joined: Aug 10, 2014
    Posts: 47

    dwleo

    yes the oil got changed after breaking and no the oil was not "all sparkly".
     
  10. Pop the valve covers for a look, if something is really off you'll see it.
     
  11. southcross2631
    Joined: Jan 20, 2013
    Posts: 4,413

    southcross2631
    Member

    Simple question. How long did the old gas set in the carb after you broke the motor in? Did you have any gas in the tank for a long time. The alcohol in the fuel will break down rubber parts and cause all kinds of problems.
     
  12. dwleo
    Joined: Aug 10, 2014
    Posts: 47

    dwleo

    Maybe a month, if that. Gas has been replaced in tank
     
  13. Still keeps coming up to me, what distributor are you using? If a GM style big cap HEI a tip that nobody usually thinks of. The pick up coil. Two wire connector to the HEI module, white and green wire with a yellow connector. Unplug that, apply an ohmmeter to the two leads and move the wires up,down, side to side, whatever and watch the needle or the digital display. If it loses any continuity, replace it. Uncommon but it can happen, I've only had one in forty plus years fail like that, but once bitten twice shy.

    Another quick and dirty way to check it is to disconnect the vacuum advance hose,start the engine. IF it runs normally, then do the ohmmeter check. If not, well another time waster tried.
     
  14. Engine man
    Joined: Jan 30, 2011
    Posts: 3,480

    Engine man
    Member
    from Wisconsin

    An oscilloscope would be handy to see if the spark is changing butI don't know if anyone has them anymore.
     
  15. Since everything when to shit after this ,,,

    I had reason to pull the dizzy-
    What reason - ?

    And relash the valves because a loosness occurred
    What the hell is a loosness ???

    Nothing had been right since.

    If you can't give us an answer to that stuff after 3-4 times asking, I'll be unsubscribing. Why bother including it in the description if there's no explanation?

    maybe the wrong tailights ?
     
    X38 likes this.
  16. Lucky someone can still spell it....
     
  17. badshifter
    Joined: Apr 28, 2006
    Posts: 3,535

    badshifter
    Member

    I'm with 31Vicky. You are not explaining what you did with the valves, but if it's hydraulic lifters it sounds like they are pumping up, which then leaves valves open causing backfire, engine dies. lifter bleeds down, start back up again runs OK until the lifters pump again causing the same problem over and over again. I still don't see where you mentioned what distributor, it also sounds like a condenser breaking down or bad if you have that in your system.
    I would start with backing all the valve adjustments off until they click, and see how it runs then.
     
  18. Are you saying that the vacuum signal at fast idle is "0"? I'm gonna go out on a limb and say that with those camshaft specs you should be seeing somewhere in the neighborhood of 14+ in. of vacuum @ idle. If this is not the case I think I would visit the camshaft and cam timing.
     
  19. Gotgas
    Joined: Jul 22, 2004
    Posts: 7,175

    Gotgas
    Member
    from DFW USA

    This was my thought. OP, please recheck the procedure for adjusting hydraulic rockers and give it a shot again.

    Another thought I had (don't laugh) is that the fuel tank is not vented properly. Like trying to suck through a pinched straw. Remove the gas cap and see if it runs better.

    Good luck!
     
  20. GreaserJosh13
    Joined: May 27, 2013
    Posts: 583

    GreaserJosh13
    Member
    from Chino

    Hey 31Vicky. I have a 1957 GMC w/ a 350 in it. I was having a lot of the same issues as you are. I'm not sure if someone else has recommended this, but if you do have an HEI distributor try replacing the ignition module/some people refer to it as the ignitor. I replaced mine and my truck fired right back up & has run great since. I was initially having intermittent problems. Here's a pic of what mine looked like. Good luck.
    Josh
    [​IMG]


    Sent from my iPhone using The H.A.M.B. mobile app
     
  21. models916
    Joined: Apr 19, 2012
    Posts: 379

    models916
    Member

    Cap and rotor spark tracking?
     
  22. dwleo
    Joined: Aug 10, 2014
    Posts: 47

    dwleo

    All is completed. Combination of lash, uh, adjustment of valves, TDC error, and timing. One would play off the other and my warped brain couldn't follow the logic trail completely enough./
    Many thanks to tinkirk who reached out with a tel number; I called, we talked and end result is the beast fires immediately and is fairly smooth.
    Thanks to all for help and especially to tinkirk.
     
    Jet96 likes this.
  23. Great news....now drive her hard till the next issue.....
    Who got it better than us...NOBODY
     
    31Vicky with a hemi likes this.

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